It is generally known in the art to treat tobacco particles to various expansion processes. These often involve subjecting the tobacco to contact with various treating gases, such as propane, ethane, carbon dioxide or chlorofluorocarbons under high pressure conditions. These treating gases typically do not chemically bind themselves with the tobacco during treatment. However, they do become absorbed into the many cavities which are found in the expanded tobacco particles. These treating gases may be held in the cavities of the tobacco particles for a significant period of time and will slowly diffuse into the atmosphere at, for example, a tobacco storage facility. Similarly, solid foods such as, for example, coffee, are often treated with volatile solvents for extracting materials such as caffeine, for adding flavors, and the like. Often, the treated food will contain trace amounts of such solvents or treating agents. Likewise, plastic films, fibers, and particles often include trace amounts of residual solvents or other volatile materials.
In all of the above cases, it is desirable to rapidly and accurately determine the amount of the residual materials retained by the solid. For example, when the treating gas is propane or another hydrocarbon, in the case of tobacco, the amount of residual gas or volatile liquid left in the treated tobacco particles is preferably accurately determined so that the potential amount of a flammable gas which may be released by the treated tobacco particles can be correctly ascertained. In the case of foods and plastics, accurate determination of residuals is important for minimization of undesirable materials which might contaminate taste or smell, or which may otherwise be undesirable. Additionally, information regarding the amount of volatile residuals held by the treated solid, e.g., tobacco, is also important for control of the treatment process.
The generally known head space analytical technique for determining the amount of residuals, such as propane in treated tobacco, requires up to 3 days to perform. This technique is dependent on the equilibration of the residual gas with the surrounding atmosphere and relies on natural molecular diffusion of the residual gas or volatile material out of particles, such as tobacco, and into the surrounding atmosphere. The primary driving force toward this equilibration is the gas concentration gradient between the treated particles and the surrounding atmosphere. Thus attempts to shorten the time period, such as by heating a tobacco sample, have not been effective to significantly reduce the time required for the equilibrium point to be reached.
It is clear that an analytical technique to evaluate gas or other volatile residuals, which takes up to 3 days to perform is not satisfactory. Thus there clearly exists a need for a process and apparatus for the measurement of volatile residuals. The process and apparatus for measurement of volatile residuals, as will be discussed subsequently, provides a solution to this problem and is clearly an advance in the art.